Many pests are difficult to control with pesticides.
Termites, for example, must have moisture and must transport food to their subterranean colonies in order to live. Consequently, they must return to the ground around or beside a building after they have eaten part of the building. If one can cut off their entry or exit, one can substantially control them. A pesticide should therefore, preferably be applied at the areas of the building where the supporting structures touch the ground, or where the termites or other pests will enter or exit. When pesticide is applied to these areas, the pests, such as termites can be controlled; but often they cannot be controlled by spraying or by application of pesticidal liquid when the areas lie under a concrete slab or similar obstruction, for example under a wooden floor which is only a few inches off of the ground. Cavities often develop beneath slabs, where the pests, including termites, can collect. They can also go from these cavities to the bottom of the slab. If the ground is porous, liquid termiticide or repellant must not only be applied in large quantities to reach the bottom of the slab, resulting in overdosing, but it may be actually impossible to fill the cavity. Further, even in the absence of cavities, liquid interjected at intervals cannot migrate horizontally in porous or moderately porous ground in the way necessary to form the continuous barrier required to effectively prevent pest passage. The above problems have been increased due to the fact that present day termite pesticides are somewhat less effective than previous termite pesticides which, unfortunately, have been discovered to have unacceptable environmental impacts. Thus, with present day termite pesticides it is even more important that they be distributed over all of the space beneath concrete slabs and the like.
Thus, there are disadvantages with liquid pesticide and with pesticide sprays.
One method which has been tried to apply pesticides is via the generation of what is commonly referred to as a dry foam. Japanese patent publication SHO 58-43050, for example, shows the use of foams which include a termite pesticide, a foaming agent, an emulsifier and water. The foam is applied utilizing apparatus which is used to chemically extinguish fires. Such an apparatus typically forms large volumes of foam in very short periods of time and the resulting foams have an expansion ratio, defined as the ratio of foam volume to volume of solution being foamed, of 100 to 1 or greater. Further, the practical example set forth in the publication shows filling a volume approximately 1.5 feet high by 27 mats, each of which is 18 square feet in area, utilizing approximately 1.75 cubic feet of solution. The total cubic volume being filled is then 1.5.times.27.times.18=729 cubic feet. Dividing this by 1.75 cubic feet gives an expansion ratio of 417 to 1. Japanese patent publication SHO 60-34901 has a similar disclosure and shows an expansion ratio of 150-500, preferably 200-400 liters per kilogram which is substantially the same per liter (liter per liter) as one kilogram of water occupies one liter in volume. The lowest expansion ratio shown, for a composition not of the invention, is less than 50 but is not otherwise specified. Japanese patent publication SHO 58-17161 is also of interest in this respect. The smallest expansion ratio (bubble multiplication) shown in the examples is 140 to 1.
Each of the aforementioned publications shows only the preparation of so-called dry foams and their application to relatively large crawl spaces. Dry foams do not flow well and, hence, cannot adequately conform to irregular ground shapes. Thus, if they were to be injected beneath building slabs, which is not contemplated by the publications and has not been attempted, they would not be capable of contacting the entire ground surface if that surface is irregular. Basically, they will simply hang out over small trenches, cavities and the like leaving the bottoms of such untouched. Since the crawl spaces treated by the foams of the publications are very large a sufficient amount of termiticide can apparently be deposited (but not on all surfaces as just discussed) in a single application, although, as a practical matter this seems doubtful and there has apparently not been an extensive commercial development of this technology.
Because of the large expansion ratio the methods of these publications are not applicable in the least to the depositing of pesticide via foams in relatively small spaces such as those below building slabs. Current state regulations require coverage of a specific amount of pesticide per linear foot (the regulations tend to specify linear foot as they envision depositing the pesticide only along the borders of slabs and the like or along trenches, etc. The regulations as to DURSBAN pesticide, a trademark of The Dow Chemical Company, is generally 15 grams per linear foot, as an example) and also require that the solution used to deliver this specific amount of coverage contain no more than a specified percent, generally between 0.5 and 1.5%, of the pesticide. To attain the specified coverage utilizing such a solution and utilizing expansion ratios as are set forth in the above described publications would require multiple fillings and dissipations of the foams or use of far larger concentrations of pesticide in solution than is allowable or safe. Furthermore, the purpose of the foam application in the publications is to allow the foam and the insecticide to be slowly absorbed into wood pillars and the like. This acts much like the conventional creosol soaking of such members to protect them from termite attack. Since the foams are purposefully made long lasting so as to allow them to be absorbed by the wooden members, multiple applications of such high expansion ratio (and relatively low pesticide concentration) foams to spaces beneath building slabs would be far too time and labor consuming so as to be practical.
British patent specification 1 274 442 is of interest in this area in that it shows the preparation of foams for being directly contacted with pests such as bacteria within closed containers or pipelines, apparently those associated with the food industry such as the milk and beer industries. Essentially, the containers or pipelines are filled with the foam which remains in place for a long enough time so that the pests can contact it directly and thereby be controlled. In the food industry deposition of residual pesticides would be highly undesirable since contamination of the food (or drink) would almost certainly occur. Hence, this publication is not concerned with foam deposition of pesticides, especially not of residual pesticides, or, if potentially residual pesticides are used it is important that they can be readily and thoroughly washed from any surfaces upon which they might be temporarily deposited. Thus, this publication is not directed to the deposition of pesticides onto the surfaces beneath slabs and the like to produce a residual pesticidal effect.
U.S. Pat. No. 4,822,613, issued Apr. 18, 1989 to A. Rodero discusses the preparation of highly stable pesticide containing water soluble foams which can be formed in situ utilizing a propellant, generally in a spray can type of arrangement. The patent discusses a foam which remained in place for a week. Control of pests is evidently via direct contact with the foam which may be generated in place in a drain pipe. The foam can be washed away when it has done its job by flushing with water. This patent is apparently not concerned with depositing a pesticide on a surface so as to provide residual pesticidal activity. The foams, to have the required long term stability, must be highly expanded dry foams since a wet foam would collapse more rapidly.
U.S. Pat. No. 3,692,512 shows the preparation of foams for applying chemicals to plants, soil or the like in the open utilizing a foam. The foam desirably is stable in the sense that it will stay moist on the plants surface for at least ten to fifteen minutes. This patent is in no way concerned with deposition of pesticide from a foam delivery system into confined spaces such as below building slabs or with providing a residual pesticidal effect in such places.
It would be highly desirable if a method were available for coating the irregular small spaces below building slabs in such a manner that the bottoms of the slabs as well as the relatively irregular ground surface below the slabs could have a pesticide effectively deposited on them, particularly a residual pesticide, and if all of this could be accomplished utilizing a solution having an allowable amount of pesticide dissolved in it to provide at least the minimum government required coverage of pesticide per unit area. The providing of such a method constitutes the main objective of the present invention.